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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

X-ray analysis of a polar plume

Polar plumes have been detected in X-rays with the Skylab S-054 experiment. Observations of one well-observed plume are analyzed and the plasma pressure is determined. An isothermal model in hydrostatic equilibrium is found to require unacceptably low temperatures. A hydrodynamic model is proposed which is consistent with earlier white light and EUV observations. Calculations indicate that the total outward mass flux in polar plumes is comparable to that in high speed solar wind streams expected from a polar coronal hole.

Ahmad, I. A.↗
NASA NTRS1978

Space shuttle main engine plume radiation model

The methods are described which are used in predicting the thermal radiation received by space shuttles, from the plumes of the main engines. Radiation to representative surface locations were predicted using the NASA gaseous plume radiation GASRAD program. The plume model is used with the radiative view factor (RAVFAC) program to predict sea level radiation at specified body points. The GASRAD program is described along with the predictions. The RAVFAC model is also discussed.

Reardon, J. E.↗
NASA NTRS1979

A nozzle boundary layer model including the subsonic sublayer usable for determining boundary layer effects on plume flowfields

A model for the boundary layer at the exit plane of a rocket nozzle was developed which, unlike most previous models, includes the subsonic sublayer. The equations for the flow near the nozzle exit plane are presented and the method by which the subsonic sublayer transitions to supersonic flow in the plume is described. The resulting model describes the entire boundary layer and can be used to provide a startline for method-of-characteristics calculations of plume flowfields. The model was incorporated into a method of characteristics computer program and comparisons of computed results to experimental data show good agreement. The data used in the comparisons were obtained in tests in which mass fluxes from a 22.2-N (5 lbf) thrust engine were measured at angles off the nozzle centerline of up to 150 deg. Additional comparisons were made with data obtained during tests of a 0.89-N (0.2 lbr) monopropellant thruster and from the OH-64 space shuttle heating tests. The agreement with the data indicates that the model can be used for calculating plume backflow properties.

Cooper, B. P., Jr.↗
NASA NTRS1979

Comparison of stack plume properties obtained from aircraft and spacecraft measurements

Landsat II imagery data and aircraft nephelometer measurements were analyzed to determine the quantitative properties of a stack plume emitted from a moderate-sized pulpmill. Aircraft measurements were obtained at several heights across the plume at 1.0, 3.0, and 6.5 km downwind from the stack, and for comparative purposes, the Landsat data were also analyzed at these same three locations and at 0.5 and 10.0 km. Overlapping, consecutive-day MSS data provided plume/no-plume radiances upwelling from the stack site. Imagery data from a 10- by 10 km region in the vicinity of the mill were normalized to correct for atmospheric, solar, and viewing angle differences for the 2 observation days, and cloud-shadow data were used to evaluate sky radiance. Particle concentrations, vertical and lateral dispersions, and plume heights determined from both the aircraft and spacecraft measurement techniques are in good agreement.

Staylor, W. F.↗
NASA NTRS1980

Aerodynamic aspects of shock containing jet plumes

Aerodynamic and acoustic measurements of shock-free and shock-containing plumes were acquired for several supersonic free-jet model nozzles. The purpose was to investigate important features of the broadband shock noise generation process. The aerodynamic measurements include the variation of shock cell spacing and strength as a function of nozzle pressure ratio, and longitudinal turbulent-mass-flux axial development as determined by a hot-film probe. In addition, correlations of the hot-film probe with a near-field microphone were obtained. These measurements provide useful information concerning the relation of peak shock noise frequency and level with variations in shock cell spacing and strength. In general, it is shown that a distinction must be made between plumes containing weak and strong imbedded shocks. Strong shocks diminish the level of emitted shock noise and influence the behavior of the jet mixing noise process. The probable location and spectral content for the shock-shear layer interaction mechanism is indicated by the correlations. Numerical inviscid plume comparisons with experimental data are also included.

Seiner, J. M.↗
NASA NTRS1980

Io - Energy constraints and plume volcanism

Observational and theoretical considerations, including near-surface energy constraints, suggest a model of Io that features a surface layer of sulfur overlying an active silicate crust. Such a model would imply frequent contact between silicate magma intrusions and the sulfur layer. This contact could produce volcanic plumes driven by high-temperature sulfur vapor. Plumes driven by sulfur vapor meet observational constraints for a wide range of possible conditions, in contrast to the special conditions required for plume generation by SO2. Characteristics of the two models are compared, and it is suggested that high-spatial-resolution infrared radiometry could identify the driving volatile.

Reynolds, R. T.↗
NASA NTRS1981

Chesapeake Bay plume dynamics from LANDSAT

LANDSAT images with enhancement and density slicing show that the Chesapeake Bay plume usually frequents the Virginia coast south of the Bay mouth. Southwestern (compared to northern) winds spread the plume easterly over a large area. Ebb tide images (compared to flood tide images) show a more dispersed plume. Flooding waters produce high turbidity levels over the shallow northern portion of the Bay mouth.

Munday, J. C., Jr.↗
NASA NTRS1981

Remote sensing of the Chesapeake Bay plume salinity via microwave radiometry

The NASA-Langley-developed L-Band microwave radiometer was used to remotely measure sea surface salinity during the Chesapeake Bay plume studies. Obtained measurements of microwave brightness temperatures of the sea surface were combined with measurements of sea surface temperature obtained with an infrared radiometer and inverted to produce corresponding values of sea surface salinity. Results from the plume measurements, which indicate the southward extent of the plume along the Virginia-North Carolina coast, are presented and discussed. Additional measurements obtained for the Delaware Bay Mouth flight, and the James River-Shelf flight, are also discussed.

Kendall, B. M.↗
NASA NTRS1981

Spatial color variations in the volcanic plume at Loki, on Io

Multicolor Voyager 1 photographs of the Loki volcanic plume, on Io, have been analyzed to determine the nature and quantity of the scattering material within the plume. This work indicates that there are two particle populations. The first population consists of particles with radius of 0.001-0.01 microns, while the second population, which is concentrated near the source, comprises particles with radius greater than 1 micron. The population of smaller particles includes most of the particulate mass in the plume. This work increases the previously estimated particulate mass (Johnson et al., 1979) and suggests that the SO2 gas spectroscopically identified by Pearl et al. (1979) may represent transient flow from the volcano instead of an atmosphere in stable equilibrium with the local surface.

Collins, S. A.↗
NASA NTRS1981

The effects of surface heat flux on plume spread and concentration - An assessment based on remote measurements

Satellite-derived surface heat-flux maps are presented in order to illustrate the large horizontal variations in surface heating that can occur over heterogeneous terrain. Results of plume-model studies published by Lamb (1978) and Willis and Deardorff (1978) were modified to show that the ground-level pollutant concentration depend closely upon the surface heat flux for the case of an elevated plume source during periods of free convection. It is suggested that remotely determined surface heat-flux patterns can be used in making plume dispersion calculations.

Carlson, T. N.↗
NASA NTRS1982

The plumes of Titan

The plasma density enhancements observed during the Voyager 1 Titan encounter are interpreted in terms of a single plume of plasma wrapped around Saturn by corotation. Consideration is given to the radial motions of the plume driven by fluctuations in solar wind pressure and the dispersal of the plasma by the centrifugal interchange instability, by heating, and by azimuthal acceleration. It is shown that Saturn cannot readily impose corotation directly on the plume and, incidentally, that the total dissipation associated with the Titan-magnetosphere interaction is insufficient to supply the power to produce the observed Titan ultraviolet airglow. A pickup velocity of 8 km/s is inferred on the basis of the observed velocity and a standing wave model. It is found that the Voyager plasma observations are consistent with the predictions of the model.

Eviatar, A.↗
NASA NTRS1983

Two classes of volcanic plumes on Io

Results of an analysis of the properties, source regions and deposits of volcanic plumes on Io are presented which suggest the presence of two plume types. Eruptions at the Aten Patera caldera in the south polar region and the Surt caldera in the far north, which were deduced to have taken place between the times of the Voyager 1 and Voyager 2 encounters from evidence of surface changes, are similar to the Pele eruption. These Pele-type eruptions are characterized by durations of from a few days to a few weeks, dark-red annular deposits of about 1400 km in diameter, temperatures of about 650 K and locations restricted to areas with large, silicate landforms. Smaller, more numerous eruptions of the Prometheus type were observed on both encounters, being characterized by durations in excess of several years, bright ringed deposits about 250 km in diameter, restriction to an equatorial location high in SO2 and temperatures less than 400 K. In addition, an intermediate type of feature was noted at either end of the linear feature Loki. Two separate mechanisms, involving SO2 and sulfur as driving sources, are proposed to account for the Pele- and Prometheus-type eruptions, respectively, and the discrete temperatures of the plumes are suggested to reflect the temperatures at which sulfur is a low-viscosity fluid.

Mcewen, A. S.↗
NASA NTRS1983

Plume base flow simulation technology

A combined analytical/empirical approach was studied in an effort to define the plume simulation parameters for base flow. For design purposes, rocket exhaust simulation (i.e., plume simulation) is determined by wind tunnel testing. Cold gas testing was concluded to be a cost and schedule effective data base of substantial scope. The results fell short of the target, although work conducted was conclusive and advanced the state of the art. Comparisons of wind tunnel predictions with Space Transportation System (STS) flight data showed considerable differences. However, a review of the technology program data base has yielded an additional parameter that may correlate flight and cold gas test data. Data from the plume technology program and the NASA test flights are presented to substantiate the proposed simulation parameters.

Roberts, B. B.↗
NASA NTRS1984

Analysis of large solid propellant rocket engine exhaust plumes using the direct simulation Monte Carlo method

A new solution procedure has been developed to analyze the flowfield properties in the vicinity of the Inertial Upper Stage/Spacecraft during the 1st stage (SRMI) burn. Continuum methods are used to compute the nozzle flow and the exhaust plume flowfield as far as the boundary where the breakdown of translational equilibrium leaves these methods invalid. The Direct Simulation Monte Carlo (DSMC) method is applied everywhere beyond this breakdown boundary. The flowfield distributions of density, velocity, temperature, relative abundance, surface flux density, and pressure are discussed for each species for 2 sets of boundary conditions: vacuum and freestream. The interaction of the exhaust plume and the freestream with the spacecraft and the 2-stream direct interaction are discussed. The results show that the low density, high velocity, counter flowing free-stream substantially modifies the flowfield properties and the flux density incident on the spacecraft. A freestream bow shock is observed in the data, located forward of the high density region of the exhaust plume into which the freestream gas does not penetrate. The total flux density incident on the spacecraft, integrated over the SRM1 burn interval is estimated to be of the order of 10 to the 22nd per sq m (about 1000 atomic layers).

Hueser, J. E.↗
NASA NTRS1984

A method for simulating 3-D aircraft flow fields with jet plume effects

The objective is to develop, demonstrate, and document a coupled flow analysis procedure for computing 3D aircraft flow fields with deflected subsonic and supersonic jet exhaust plumes. The PNS plume code was transferred to the Ames computer facility for execution on the Cray computer. No problems were encountered when installing this code. The Bower's test case is currently being run. This case is being used to fine tune the procedure for coupling the plume code to PANAIR.

Source record↗
NASA NTRS1985

A tandem mirror plasma source for a hybrid plume plasma propulsion concept

This paper describes a tandem mirror magnetic plasma confinement device to be considered as a hot plasma source for the hybrid plume rocket concept. The hot plasma from this device is injected into an exhaust duct, which will interact with an annular layer of hypersonic neutral gas. Such a device can be used to study the dynamics of the hybrid plume and to experimentally verify the numerical predictions obtained with computer codes. The basic system design is also geared toward being lightweight and compact, as well as having high power density (i.e., several kW/sq cm) at the exhaust. This feature is aimed toward the feasibility of 'space testing'. The plasma is heated by microwaves. A 50 percent heating efficiency can be obtained by using two half-circle antennas. The preliminary Monte Carlo modeling of test particles result reported here indicates that interaction does take place in the exhaust duct. Neutrals gain energy from the ion, which confirms the hybrid plume concept.

Yang, T. F.↗
NASA NTRS1987

An analytical and experimental investigation of resistojet plumes

As a part of the electrothermal propulsion plume research program at the NASA Lewis Research Center, efforts have been initiated to analytically and experimentally investigate the plumes of resistojet thrusters. The method of G.A. Simons for the prediction of rocket exhaust plumes is developed for the resistojet. Modifications are made to the source flow equations to account for the increased effects of the relatively large nozzle boundary layer. Additionally, preliminary mass flux measurements of a laboratory resistojet using CO2 propellant at 298 K have been obtained with a cryogenically cooled quartz crystal microbalance (QCM). There is qualitative agreement between analysis and experiment, at least in terms of the overall number density shape functions in the forward flux region.

Zana, L. M.↗
NASA NTRS1987

An analytical and experimental investigation of resistojet plumes

As a part of the electrothermal propulsion plume research program at the NASA Lewis Research Center, efforts have been initiated to analytically and experimentally investigate the plumes of resistojet thrusters. The method of Simons for the prediction of rocket exhaust plumes is developed for the resistojet. Modifications are made to the source flow equations to account for the increased effects of the relatively large nozzle boundary layer. Additionally, preliminary mass flux measurements of a laboratory resistojet using CO2 propellant at 298 K have been obtained with a cryogenically cooled quartz crystal microbalance (QCM). There is qualitative agreement between analysis and experiment, at least in terms of the overall number density shape functions in the forward flux region.

Zana, Lynnette M.↗